The invention relates to agricultural equipment comprising one or more rollers provided with a series of tyres threaded onto a tubular horizontal support, these tyres having a profile of a selected shape, particularly a dome-shaped profile, enabling a series of parallel furrows to be formed in the earth.
Rollers of this kind are described for example in the publications FR-A-2763279 and FR-A-2841733, in the name of the present Applicant.
These documents describe in detail the special tyres used, each of which comprises a central sleeve adapted to be threaded onto a tubular horizontal support, and a tread portion with a dome-shaped profile connected to the sleeve by two sidewalls that define an enclosed uninflated internal space which is annular in shape. This configuration ensures that the tread of the tyre is not flattened too much, while giving it sufficient flexibility to enable it to undergo deformation and be self-cleaning.
These rollers are conventionally drawn by a tractor, being placed behind ground working tools, while the roller may optionally be followed by other working tools.
A typical application is that of rollers for seed drills in which the tractor pulls a machine formed by a combination of semi-trailed tools comprising: groundworking tools; next, the roller with its dome shaped tyres which create furrows in the ground previously prepared by the tools; then seed drills which deposit grains or seeds in the furrows formed by the passage of the roller; and finally burying tools for burying the seeds.
In other applications, the roller equipped with its dome shaped tyres is placed behind groundworking tools, for example in order to break the stubble on the ground after harvesting. In this case, the roller is not followed by tools and serves essentially to level the ground.
In all the embodiments proposed hitherto, the tyres are threaded onto a large-diameter single central cylindrical tube constituting the tubular structure supporting the series of tyres.
However, by its nature, this massive structure has a considerable weight which does not contribute to the efficacy of the tool: in fact, for a seed drill, for example, it is important not to compact the ground but to form furrows in ground that has previously been prepared.
Moreover, the considerable mass of the roller gives it a substantial inertia. This inertia may be a problem when the agricultural machinery is travelling on roads, and when the roller is not supported by a raising mechanism, it is necessary to provide power braking systems, as described for example in the publication FR-A-2841733 in the name of the present Applicant.
Lastly, the final retail price of the roller is substantially increased by the costs of the materials and labour needed to manufacture this large-diameter tube.